There are many different types of universal joints. One type of universal joint includes a telescoping constant velocity joint, sometimes referred to as a tripot universal joint. Telescoping constant velocity joints are typically employed in automotive axial drive shafts, and especially in front-wheel-drive vehicles between the transaxle differential and the driving wheel. The telescoping constant velocity joint transmits a torque at various speeds, angles and telescopic positions between shaft members.
As shown in FIGS. 7 and 8, related art telescoping constant velocity joints 20′ may include a first shaft member 22′ and a second shaft member 24′. The first shaft member includes a housing 28′. The housing defines a plurality, but preferably three, internal guide channels. The guide channels extend along and parallel to a longitudinal axis of the first shaft member 22′. The second shaft member 24′ includes a spider 40′ disposed at one end of the second shaft member 24′. The spider 40′ is disposed within the housing 28′ of the first shaft member 22′. The spider 40′ includes a plurality, but preferably three, trunnions 42′. The telescoping constant velocity joint includes a plurality of ball assemblies 52′. One of the ball assemblies 52′ is rotatably mounted to each of the trunnions 42′, and is disposed in one of the guide channels in rolling engagement with the guide channel. The ball assemblies may include inner balls 54′, and outer balls 56′, and a plurality of roller elements 58′ disposed between the inner balls 54′ and the outer balls 56′. The roller elements 58′, in combination with the inner balls and the outer balls, effectively create a needle bearing assemblies. Accordingly, the roller elements 58′ reduce rolling friction between the inner balls 54′ and the outer balls 56′.
These telescoping constant velocity joints 20′ function well, but are restricted to operating within a predetermined angular range of articulation, illustrated as angular range 50′ in FIG. 7, where the joint maintains a predetermined or nominal joint condition where the inner ball 54′ is rotatable about the centroid 70′ of the trunnion 42′ with the inlet diameter 72′ disposed axially inwardly of the centroid 70′ with reference to the spider center 44′, i.e., closer to the spider center 44′, as shown in FIG. 8. If the first shaft member 22′ and the second shaft member 24′ are articulated beyond this range of articulation in an angular range of over-articulation, illustrated as angular range 51′ in FIG. 7, then at least one of the ball assemblies 52′ may separate from the trunnion 42′, as shown in FIG. 7. Once the ball assembly 52′ is separated from the trunnion 42′, the ball assembly 52′ will not reattach itself to the trunnion 42′ when the joint is returned within the predetermined angular range of articulation 50′ (FIG. 9) and thus the detachment is irreversible and the joint is incapable of returning to the nominal condition (FIG. 8) where the trunnion 42′ and convex outer surface 48′ are disposed inside the inlet diameter 72′ and along inner surface 62′ of inner ball 54′ as it rotates. Rather, the centroid 70′ of the trunnion 42′ will be disposed outside the inlet diameter 72′ and inner surface 62′ of inner ball 54′ will rotate on only a small bearing surface on the upper portion of trunnion 42′ as shown in FIG. 9. Once the universal joint 20′ has experienced an over-articulated condition, the joint must be disassembled to re-attach the detached ball assembly 52′, particularly the inner surface 62′ of the detached inner ball 54′ onto the convex outer surface 48′ of trunnion 42′, i.e., the spider 40′ must be removed from within the housing 28′ to re-attach the ball assembly 52′ onto the trunnion 42′, which may also necessitate removing the universal joint from its application, such as the drivetrain of a vehicle.
Therefore, it is desirable to develop universal joints that are protected from such irreversible detachment of the ball assembly in response to over-articulation of the joint, particularly detachment that requires disassembly of the joint to return the detached ball assembly and joint to a nominal condition.